Adam,
 
Rather frustratingly I still can't get this working within my project.  I am not generating the ASP.NET ScriptManager and  UpdatePanel controls dynamically like within the InitAjaxPanel() method within the examples.  My control hierarchy is as follows
Site.Master
    ContentPlaceHolder
ChildPage
    ScriptManager
        AjaxTabContainer (Ajax Control Toolkit)
            AjaxTabPanel (Ajax Control Toolkit)
                UpdatePanel
                    ContentTemplate
                        CuteWebUI:Uploader
 
 
I was thinking it could be an issue with the AjaxUploader being within the Ajax Control Toolkit Tab Panel so I pulled the AjaxUploader out to reside within an Update Panel within the ScriptManager control but still no luck.
Could you explain exactly how to initialise the AjaxUploader control when simply adding it to the page as opposed to the dynamic loading as within the Demos?

Cheers,

ll